Spectro-chemical Studies of Complexes of Pb(II) with Triazole at Different pH(s)

Introduction

The triazoles are of great biological ^1-5 significance. It is also powerful fungicide. The   present   communication   reports   the  results of   the spectro-photometric studies of the complexes of Pb(II) with 5-mercapto-4-amino-3-methyl 1, 2, 4 Triazole prepared ^6-8.

Isolation of the Complexes

A mixture of hot aqueous solution of lead acetate and ligand were taken in the ratio of 1:2. By adding NaOH the pH of the mixture 4, 7 and 11 adjusted. The mixtures were refluxed till complexes were precipitated. The complexes obtained were further treated with ethanolic solution, then ether, then were filtered by suction, washed with ethanol and ether, dried at 100⁰C in the electric oven for several hours.

The complexes were found insoluble in most of the organic solvents. method using Hg [Co(SCN)₄] as celebrant. IR spectra of the complexes were recorded.

Table 1: Analytical and physical data of ligand and complexes

Compounds	Colour	Analytical found/calulated					……. M.P.(C)
		N	C	H	S	M
Ligand (L) 5-Mecrepto -4-amino-3-methyl 1-2-4-triazole	Faint Yellow	43.07 42.82	27.49 27.69	4.61 4.28	24.61 24.38	–	–
[Pb(CH3COO)2L2]. 3H2O	White	17.49 17.38	18.69 18.64	3.67 3.75	– –	32.39 32.41	2100
[Pb(CH3COO)2L2]. 2H2O	White	16.80 16.79	17.02 17.24	2.18 2.10	–  –	40.98 41.6	190
[Pb(CH3COO)2L2]. H2O	White	18.56 18.46	19.78 19.89	3.21 3.31	– –	34.25 34.35	170

 

Result and discussion

IR. Spectra of the Complexes

A comparison of IR. spectra of ligand and Pb(II) complexes indicates following facts ^9-12.

In all Pb (II) complexes strong bands at 3180 and 3060cm^-1 in the spectrum of the ligand are not present in the spectrum of the complexes which shows that there are coordination between N-atom of NH₂ group of the ligand and Pb (II) ion.

The 3120 cm^-1 band of the ligand assigned as vNH₂ get shifted to 3080cm^-1 in the spectrum of the complex this further confirm. NH₂ group of the ligand coordinated with Pb (II).

The 2515 cm^-1 weak band in the spectrum of the ligand is due to vS-H made of vibration this band disappeared in the spectrum of complexes so this form of the ligand in coordinated to Pb(II) ion in the complexes or the hydrogen atom of the SH group has been replaced by Pb(II) ion.

The medium band at 1295 cm^-1 in the spectrum of the ligand is due to vC=S, this band get red shifted to 1255 cm^-1 in the spectrum of the complex. This further supports coordination of the ligand to its S-atom.

The vC^…..S is observed at 984cm^-1 in the spectrum of the ligand. This band is red shifted to 965cm^-1 in the spectrum of the complex which confirms coordination of the ligand to the Pb (II) Ion through sulphur.

In the far IR spectrum of the complexes^13-15 a new band observed at 521cm^-1 due to plane mode of vibration of lattice water.

In the IR spectrum of the complexes new bands at 520, 265, 235 and 215cm^-1 assigned as  a Pb^—–N, 260cm^-1  va Pb^—–N and 230 & 210cm^-1 assigned as Öa Pb^—–S.

On the basis of above discussion the octahedral  structure  of the complexes assigned.

The author wish to express this sincere thanks to CDRI, Lucknow for recording spectrum and authority of College of Commerce for providing facilities.

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